Desulfurization using hydrogen chloride and hydrogen



J. E. ERMA'N 3,509,045

DESULFURIZATION USING HYDROGEN CHLORIDE AND HYDROGEN April 28, 1970 Filed July 11, 1968 OOON 7 OONF 00 CON 0 INVENTOR JAMES E. ERMAN AdToRNEYs United States Patent U.S. Cl. 208225 6 Claims ABSTRACT OF THE DISCLOSURE Heavy oils are desulfurized by contacting the oil with hydrogen and hydrogen chloride at a hydrogen chloride partial pressure of at least 50 p.s.i.g. at a temperature between 600 and 950 F.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to desulfurization processes. More particularly, this invention relates to an improved method of desulfurizing hydrocarbon oils in the presence of hydrogen. Still more specifically, the present invention is directed toward a process for desulfurizing heavy oils such as petroleum crude oils, heavy gas oils obtained from atmospheric or vacuum distillation of crude or other oils, solvent deasphalted oils, and in preferred embodiments the invention relates to desulfurization of heavy oils such as atmospheric distillation column bottoms product (crude oil residuum), vacuum distillation column bottoms product (vacuum residuum), and crude oils obtained from shale or tar sands, etc., all of which commonly contain a significant quantity of asphaltic material, high concentrations of sulfur compounds and a significant quantity of organometallic compounds.

Prior art In general, the presence of sulfur or sulfur-containing compounds is highly undesirable in heavy oils such as petroleum crude oils and petroleum residuum fractions. Many of the valuable properties of these materials are seriously impaired by the presence of sulfur compounds which results in a downgrading of their commercial value. Largely because of increasing population, it has become necessary in many applications to reduce the sulfur level of fuel oils to low levels so that when the fuel oil is burned there is only a small amount of sulfur dioxide formed with the result that part of the air pollution problem attributable to sulfur dioxide is minimized. Many of the currently used fuel oils are obtained from crude oil residua and other heavy oil cuts which contain asphaltic and metallic compounds which make these fractions of the crude oil very difiicult to desulfurize by processes in accordance with the prior art.

In the past numerous processes have been employed to eliminate undesirable sulfur compounds. One type of process involves physical extraction with a liquid solvent such as sulfuric acid, sulfur dioxide, furfural and the like. Another type of process removes the sulfur compounds by adsorption on suitable materials, for example activated bauxite, activated charcoal or an activated clay. A further type of process converts objectionable forms of sulfur compounds, such as mercaptans, into less harmful forms such as disulfides and polysulfides by various chemical treatments, for example plumbite treatments, hypochlorite treatments and copper chloride treatments. In those processes for converting the mercaptans into less harmful forms, subsequent processing must be applied to eliminate the less harmful forms of the sulfur compounds in order to obtain a hydrocarbon fraction of reice duced sulfur content. It is to be noted that the above processes are used essentially exclusively for the treatment of naphtha, gasoline, and other light hydrocarbon distillate fractions. With feedstocks of high molecule weight, such as heavy oils, a large portion of the material is in the form of hydrocarbonaceous molecules containing at least one sulfur atom, and, particularly, in selective separation processes, the removal of the sulfur-containing compounds would result in low product yield.

Hydrogen chloride has been used, generally together with various metal salts, for treatment of light hydrocarbon fractions such as naphtha, gasoline or distillates. For example, U.S. Patent 1,970,283 discloses a vapor phase process directed to the treatment of cracked hydrocarbon oil vapors such as gasoline boiling range fractions. According to the process of U.S. Patent 1,970,283, gum forming components are removed and sulfur contents are reduced by subjecting the light hydrocarbon vapor in heated condition to the action of hydrochloric acid while in contact with a solid mixture of a salt of a metal above and a salt of a metal below hydrogen in the electro-chemical series.

Somewhat similar is U.S. Patent 1,970,284, which discloses a liquid phase process for refining gasoline-containing distillate to reduce the gum and sulfur content thereof by subjecting the distillate at elevated temperatures to the action of hydrochloric acid in the presence of a contact agent such as a zinc ore under sufficient pressure to maintain the distillate in liquid phase during the treatment. U.S. Patent 1,970,284 discloses that it is beneficial to maintain sufficient pressure to insure substantially liquid phase conditions. It is postulated in U.S. Patent 1,970,284 that the reactions taking place with respect to sulfur according to the process of U.S. Patent 1,970,284 are of two types; the first involving polymerization of sulfur compounds along with polyunsaturated hydrocarbons so that the sulfur appears in the heavy polymers which are removed from the process as a waste stream; the second involving a preliminary combination of organic sulfur with a metal to form metal sulfide which is later decomposed with hydrochloric acid to evolve hydrogen sulfide as a gas. U.S. Patent 1,970,284 relates only to light hydrocarbon fractions such as gasoline and motor fuel boiling range hydrocarbons obtained as straight run distillation products from petroleum crude oil or obtained by cracking heavier fractions of hydrocarbon oils. In the process of U.S. Patent 1,970,284 no hydrogen gas is used and generally at least a portion of the sulfur compounds are removed as polymers which is generally a waste product.

Another type of process which has been found particularly useful for the treatment of distillate fractions such as gas oil is hydrocatalytic desulfurization, which comprises passing an oil together with hydrogen under pressure over a suitable catalyst at elevated temperature in order to eliminate sulfur atoms from the sulfur-containing compounds in the form of hydrogen sulfide. The object of the catalytic hydrodesulfurization type processes is to sever the carbon-sulfur linkages in the sulfur-containing compounds, eliminating the sulfur in the form of hydrogen sulfide while at the same time hydrogenating the hydrocarbon fragments left as a result of the desulfurization reaction. Temperatures typically employed in desulfurization processes to sever the carbon-sulfur linkages, etc. generally are between about 600 and 950 F., preferably between about 650 and 850 F. It has been found, however, that in order to effect appreciable reductions in the sulfur content of high molecular weight material, particularly for the heavy oils such as whole crude oil, residuum, etc., mentioned previously, the conditions required for such hydrogen treatments are severe 3 and the catalyst life is greatly shortened by metal and coke deposit formation.

SUMMARY OF THE INVENTION According to the present invention, a process is provided for desulfurizing a heavy oil in the presence of hydrogen at an elevated temperature between 600 and 950 F. and hydrogen partial pressure between 100 and 5000 p.s.i.g. wherein the improvement is made which comprises contacting the heavy oil with hydrogen chloride at a hydrogen chloride partial pressure of at least 50 p.s.i.g.

This invention is based, among other factors, on the discovery that heavy oils can be successfully hydrodesulfurized by using hydrogen'chloride together with hydrogen. The process of the present invention has advantages compared to catalytic hydrodesulfurization using hydrogen because the present process does not require the presence of small catalyst particles. Previous attempts to remove sulfur from residual stocks, by catalytic hydrogenation at moderate pressures, for example 1000 to 3000 p.s.i.g., have resulted in extremely rapid deactivation of the catalyst by metal and coke deposition on the catalyst due to the metalliferous and asphaltic contaminants in such stocks. In the present invention inert particles providing contact surface area for the reactants may be used but they are not required. Also, in the process of the present invention it is not necessary to use small catalyst particles such as are typically used in catalytic hydrodesulfurization processes. The process of the present invention may be operated at moderate hydrogen pressures, for example 1000 to 3000 p.s.i.g.

The present invention is based on the further finding that higher partial pressures of hydrogen chloride in the presence of hydrogen result in deeper desulfurization of the heavy oils, particularly when partial pressures for hydrogen chloride above 50 p.s.i.g. are employed. In the present invention it is not necessary that the heavy oil being treated be in the liquid phase. Generally, at the temperatures employed, that is 600 to 950 F., and in the presence of large amounts of hydrogen, the heavy oil will be in both the vapor and liquid phase.

As indicated above, it has been found that the depth of desulfurization of heavy oils such as crude oil residuum is improved when the partial pressure of hydrogen chloride is maintained above 50 p.s.i.g. Furthermore, it has been found preferable to use hydrogen chloride partial pressures of at least 150 p.s.i.g. Thus, in a preferred embodiment of the present invention, a process is provided for converting organic sulfur compounds contained in a heavy oil such as crude residuum to sulfur-free organic compounds and hydrogen sulfide which process comprises contacting the oil with hydrogen chloride at a partial pressure of hydrogen chloride of at least 150 p.s.i.g. and with hydrogen at a partial pressure between 100 and 5000 p.s.i.g. for at least one hour residence time in a reaction means at a temperature between 600 and 950 F.

The process of the present invention may be carried out batchwise or in a continuous manner. If the desulfurization is carried out by a continuous flow scheme, then the residence time in the reaction means, for example one or more reactor vessels, should be between about one-half hour and 10 hours, preferably between one-half hour and 3 hours. Thus the liquid hourly space velocity (LHSV) is preferably between 2 and 0.333.

EXAMPLES The drawing in this patent application shows the effect of increasing partial pressure of the hydrogen chloride on the percentage desulfurization for Midway crude oil residuum. The curve shown on the drawing is based on sulfur removal obtained at a total pressure of about 2000 p.s.i.g., 750 F., and 1 hour residence time. The Midway crude oil residuum had the following properties: gravity, 11.6 API; sulfur content, 1.18 weight percent; nitrogen,

about 0.88 weight percent; chloride, 0.21 weight percent; oxygen, 2.9 weight percent.

ASTM D1160 distillation Vol. percent distilled: Temperature F.

Using no hydrogen chloride, a portion of the Midway crude oil residuum was heated to and maintained at 750 F. for one hour under a hydrogen gas pressure of 2000 p.s.i.g. To provide contact of the crude oil residuum in the pressure vessel with the hydrogen the residuum was constantly stirred. After the one hour residence period the vessel was depressurized and hydrogen and hydrogen sulfide were removed as gases. The residuum was then analyzed for sulfur content by X-ray fluorescence. It was found that the initial sulfur content of 1.18 weight percent was reduced to 0.87 weight percent for a percent desulfurization of 26.3 weight percent.

Using the same conditions as immediately above except that hydrogen chloride was introduced until the partial pressure of hydrogen chloride was 150 p.s.i.g. (hydrogen partial pressure was about 1900 p.s.i.g., thus making the total pressure 2050 p.s.i.g.), sulfur content of a second portion of Midway residuum was reduced from 1.18 weight percent to 0.43 weight percent for a desulfurization of 63.5 weight percent. Thus, using hydrogen chloride under pressure in the presence of hydrogen resulted in an unexpectedly large increase in desulfurization of the residuum. The percent increase in desulfurization by using hydrogen chloride versus using only hydrogen at 750 F. was about As before, the sulfur was removed as hydrogen sulfide when the reaction mixture was depressurized. The percent conversion to hydrocarbon boiling below 650 F. was about 10 percent which was essentially the same percentage conversion as when only hydrogen was used.

By further increasing the partial pressure of hydrogen chloride even greater improvement is made in the amount of desulfurization. For example, at 900 p.s.i.g. hydrogen chloride partial pressure and 1070 p.s.i.g. hydrogen partial pressure the sulfur was reduced from 1.18 weight percent to 0.27 weight percent for the Midway crude oil residuum. Thus the percent desulfurization was 77. This was verified by another test run at 900 p.s.i.g. hydrogen chloride partial pressure and hydrogen partial pressure of 913 p.s.i.g., which resulted in 80.5 percent desulfurization. The percent conversion to hydrocarbons boiling below 650 F. for the 80.5 percent desulfurization run was 26.4 percent (versus 10% for p.s.i.g. hydrogen chloride), thus illustrating that at higher hydrogen chloride partial pressures increased hydrocracking is obtained.

In an example of still higher hydrogen chloride partial pressure, 1700 p.s.i.g. hydrogen chloride was obtained using mercuric chloride as a starting material, as it was found that the mercuric chloride in the presence of hydrogen at 750 F. was reduced to mercury plus hydrogen chioride. In the presence of the thus generated 1700 p.s.i.g. hydrogen chloride and the resulting hydrogen partial pressure of about 560 p.s.i.g., the sulfur was reduced from 1.18 weight percent to 0.20 weight percent thus obtaining about 83% 'desulfurization of the Midway residuum under the standard test conditions of one hour residence time and 750 F. The percent conversion to hydrocarbons boiling below 650 F. increased to 39.6, thus again illustrating increased hydrocracking as a result of the increased hydrogen chloride partial pressure.

It can be seen from the curve shown in the drawing that a particularly large increase in desulfurization is obtained by adding hydrogen chloride to the hydrogenresiduum oil mixture to obtain a hydrogen chloride pressure of between and 150 p.s.i.g. If the hydrogen chloride partial pressure is increased from 0 p.s.i.g. to 50 p.s.i.g., the desulfurization is expected to increase for Midway crude oil residuum from about 26 weight percent to between about 41 and 45 weight percent desulfurization, which represents a 58 to 73 percent improvement in desulfurization.

Use of hydrogen chloride under substantial superatmospheric pressure was also found to be effective in desulfurization of very refractory and diflicult to desulfurize (compared not only to light oils but also compared to more typical crude oil residua) residua such as Safaniya crude oil residuum boiling above about 650 F. at atmospheric pressure. The properties of the Safaniya residuum were as follows: gravity, 12.9 API; sulfur content,

4.1 weight percent; nitrogen, 0.3 weight percent; oxygen,

0.56 weight percent;

ASTM D1160 distillation Vol. percent distilled: Temperature, F. Start 526 u 680 751 826 886 33 900 The Safaniya residuum was contacted with hydrogen chloride at a partial pressure of about 980 p.s.i.g. and hydrogen with a partial pressure of about 1070 p.s.i.g. The Safaniya residuum was heated to and then maintained at 750 F. for one hour while being stirred in the presence of the hydrogen chloride and hydrogen. 29% conversion to material boiling below 650 F. was obtained. As in the other runs, the gaseous hydrogen sulfide which was formed was removed after the one hour reaction period by depressurization. Loss of light hydrocarbons during the depressurization is substantially avoided by chilling the gases that are removed by depressurization so as to condense the light hydrocarbons. In this experiment with Safaniya residuum the sulfur content of the desulfurized residuum material boiling below 650 F. was 1.69 weight percent, and the sulfur content of the desulfurized residuum material boiling above 650 F. was 2.14 weight percent. Thus the overall percent desulfurization was 51 weight percent.

In contrast, a number of metal chlorides, including zinc chloride, were tried in the presence of 2000 p.s.i.g. hydro gen at 750 F. in attempts to desulfurize the Safaniya crude oil residuum, but the greatest amount of desulfurization obtained using the metal chlorides was 18 weight percent.

Although various specific embodiments of the invention have been described and discussed, it is to be understood that they are meant to be illustrative only and not limiting. Certain features of the process may be changed without departing from the spirit or essence of the invention. It is apparent that the invention has broad application to the desulfurization of heavy hydrocarbonaceous materials. Accordingly, the invention is not to be construed as limited to the specific embodiments illustrated but only as defined in the following claims.

I claim:

1. In a process for desulfurizing a heavy oil in the presence of hydrogen at elevated temperature between 600 and 950 F. and hydrogen partial pressure between 100 and 5000 p.s.i.g., the improvement which comprises contacting the heavy oil with hydrogen chloride at a hydrogen chloride partial pressure of at least 50 p.s.i.g.

2. A process according to claim 1 wherein the hydrogen chloride partial pressure is at least 150 p.s.i.g.

3. A process according to claim 1 wherein the heavy oil which is desulfurized is a crude oil residuum or a vacuum residuum.

4. A process for converting organic sulfur compounds contained in a heavy oil to sulfur free organic compounds and hydrogen sulfide which comprises contacting the oil with hydrogen chloride at a partial pressure of hydrogen chloride of at least 150 p.s.i.g. and with hydrogen at a hydrogen partial pressure between 100 and 5000 p.s.i.g. for at least one hour residence time in a reaction means at a temperature between 600 and 950 F.

5. A process according to claim 4 wherein the hydrogen chloride partial pressure is maintained between 150 p.s.i.g. and 1700 p.s.i.g.

6. A process according to claim 4 wherein at least volume percent of the heavy oil consists of organic compounds boiling above 650 F. at atmospheric pressure.

References Cited UNITED STATES PATENTS 1,445,688 2/1923 Hyatt 208- 2,055,027 9/1936 Day 208225 3,085,061 4/1963 Metrailer 20898 1,970,283 8/1934 Day 208-225 1,970,284 8/1934 Day 208-225 DELBERT E. GANTZ, Primary Examiner J. M. NELSON, Assistant Examiner US. Cl. X.R. 208209 

